Extracorporeal membrane oxygenation provides life support for coronavirus patients suffering respiratory failure.
After all other conventional treatments have failed, extracorporeal membrane oxygenation (ECMO) life support can be a coronavirus patient's last hope for recovery.
ECMO is a form of life support that features a machine that performs essential functions of the heart and lungs. The ECMO machine is connected to a patient through plastic tubes that are placed in large veins and arteries in the legs, neck, or chest, according to the American Thoracic Society. Blood flows through the ECMO machine, which adds oxygen to the blood and removes carbon dioxide, then the blood is returned to the patient.
ECMO technology has advanced significantly since it was developed in the early 1970s, but it is a high-risk intervention, says Jonathan Haft, MD, ECMO medical director at Michigan Medicine, and an associate professor in cardiac surgery at University of Michigan Medical School.
"ECMO still is a last-ditch effort. ECMO is a challenging therapy. It requires expertise, experience, carefully established policies, teamwork, and quality assurance reviews. Centers that do not have a lot of experience doing ECMO are unlikely to have a lot of success. You can't just buy the equipment and start doing it," he says.
Michigan Medicine recently discharged the health system's first coronavirus survivor who underwent ECMO, Haft says.
"It was a typical ECMO course. The patient was gravely ill and at imminent risk of death when the ECMO decision was made. He was supported well on ECMO and eventually liberated from ECMO, then he was liberated from a ventilator and was eventually well enough to go home independently to his family. The belief is that his long-term life expectancy will be close to normal."
So far, 15 adult coronavirus patients have undergone ECMO at Michigan Medicine, and Haft predicts at least half of the patients will survive. "I expect our survival rate will be over 50%—probably over 60%. That survival rate would be consistent with what we have seen in other adult patients who are treated with ECMO for all-cause respiratory failure."
Most ECMO patients are on the life support machine in an ICU for about nine days, and the average hospital length of stay is more than a month, Haft says.
He says there are four primary complications:
- Clotting that can form on artificial surfaces
- Bleeding because patients are given high levels of blood thinners
- Skin infections where the large-bore tubes are inserted
- Hospital-acquired infections linked to the extended length of stay
Graphic credit: American Thoracic Society
Selecting coronavirus patients for ECMO
At Michigan Medicine, Haft says five main factors are considered before a coronavirus disease 2019 (COVID-19) patient is placed on ECMO:
- Advanced age can be disqualifying. "We do not have an age cutoff for ECMO; but the older you get, the more discerning we are about appropriateness in candidacy," he says.
- Co-morbidities are assessed. "We factor in other medical problems—does the patient have diabetes, chronic kidney failure, or cirrhosis of the liver? Does the respiratory failure represent an exacerbation of an established and irreversible chronic lung disease? In other words, if a patient has baseline emphysema or baseline pulmonary fibrosis with COVID-19, they may not be an appropriate candidate."
- Overall functional status, which is a surrogate for other medical problems and age combined, is a factor. Elements of functional status include debilitation, ability to live independently, and dependence on assistive devices.
- Duration of mechanical ventilation can be a contraindication. "Once we get beyond seven days on mechanical ventilation, the likelihood of survival starts to drop," he says.
- Physicians also consider the lung injury score, which assesses the dependence on mechanical ventilation, the stiffness of the lungs, and the appearance of the lungs on chest X-ray. "These are all markers of the severity of lung injury," he says.
ECMO is resource-intense and the COVID-19 pandemic is resource-draining, so patient selection requires rigorous consideration, Haft says. "In the context of COVID-19 and the volume of patients, the resources have become scarce—not just ECMO resources, but also ICU beds, ventilators, nurses, and blood bank supplies. With scarcity throughout the institution, we are trying to be even more thoughtful about ECMO candidates."
The patient selection process involves life-or-death calculus, he says. "You do not draw a line on patients, but you put all of the factors together and they give you a likelihood of recovery. Our selection criteria are based on the likelihood of meaningful recovery. The alternative is death, but the one thing that can be worse than death is futility—depending on life support for a long period of time without meaningful benefit of survival."
At Michigan Medicine, the decision to place a COVID-19 patient on ECMO usually involves at least two physicians, Haft says. "When I am not on call, the ECMO physician who is on call will contact me to discuss the individual case. If we are borderline on whether ECMO is appropriate, then I will typically call two or three of my senior partner colleagues and we will have a group discussion about the case."
Role of ECMO in the pandemic
With limited resources, ECMO will not play a pivotal role in the COVID-19 pandemic, Haft says.
"From an epidemiologic perspective, ECMO's impact will probably be too low to measure. The number of people in the U.S. who have COVID-19 are in the hundreds of thousands, and the number of patients who are going to get ECMO is in the hundreds. So, epidemiologically ECMO is not going to be a solution. However, on an individual basis, there is no question that ECMO will save lives."
Christopher Cheney is the senior clinical care editor at HealthLeaders.
ECMO is a form of life support that can sustain patients with severe respiratory failure until they recover from their illness.
At Michigan Medicine, more than half of coronavirus patients who undergo ECMO are expected to survive.
When selecting coronavirus patients for ECMO, several factors are considered such as age, co-morbidities, and functional status.